5x^2+25x-111=-x^2-8x+9

5x^2+25x-111=-x^2-8x+9, 6x^2+33x-120=0, 2x^2+11x-40=0, D=11^2-4×2×(-40)=121+320=441, x1=(-11-корень 441)/(2×2)=(-11-21)/4=-32/4=-8, х2=(-11+корень 441)/(2×2)=-11+21)/4=10/4=2,5. Х1=-8, х2=2,5.

5x^2+25x-111=-x^2-8x+9

 5x^2+25x-111+x^2+8x-9=06x^2+33x-120=0D=33^2*4(-120)*6=1089+2880=3969x1=(-33-63):12=-8x2=(-33+63):12=2.5